Benefit is hereby claimed of U.S. Provisional Application No. 60/453,536 filed on Mar. 11, 2003.
1. Field of the Invention
The present invention relates generally to valves and, more particularly, to apparatus and methods for a valve telescoping seat assembly.
2. Description of the Background
Telescoping seat assemblies have been known for use in gate valves for some time. One advantage of this type of seat assembly is the ability to provide a force on the seats and valve body that varies due to pressures encountered. In this way, one is assured of a good seal with a wide range of pressures. Another advantage of one exemplary type of telescoping seat assembly is the ability to provide both an upstream and a downstream seal. This provides two working seals that thereby increase the reliability of operation as compared with most other valves that utilize only one seal, such as a downstream seal. Another advantage is that friction due to movement of the gate may be kept at a minimum because the sealing force exerted by the seat assemblies automatically adjusts as necessary to securely maintain a gas-tight seal but is decreased at lower pressures to reduce friction wear.
Especially for the case of the upstream seal, it may be desirable to de-energize the seals after operation by releasing any trapped pressure that may become trapped between any sealing assemblies during valve operation and/or in the cavity of the valve. While the seals are de-energized in normal operation, it would be desirable to provide a means for de-energizing seals under virtually any type of conditions and in which the seals may include any type of seal arrangement.
Unidirectional seals may be made of non-elastomeric and non-permeable materials that will operate under much wider ranges of temperatures, fluids, and pressures. However, such seals do not create a reliable seal as easily as elastomeric O-rings. The tolerances must be much tighter and the surfaces cannot tolerate imperfections. The seals may be more sensitive to debris than O-ring seals.
The original telescoping gate valve seat assembly to simultaneously provide both upstream and downstream sealing is shown in U.S. Pat. No. 4,878,651, issued Nov. 7, 1989, to F. W. Meyer, Jr., developed at Worldwide Oilfield Machine, Inc., which is incorporated herein by reference and discloses a through conduit gate valve apparatus with a valve seat assembly that is field-maintainable and which prevents the occurrence of pressure lock. Each valve seat assembly includes a retainer ring fixed in the valve body and a pressure responsive seat ring that seals with the gate member. The seat ring is responsive to fluid pressure in the valve flow passageways for maintaining and enhancing the face seal with the gate and simultaneously to fluid pressure in the valve chamber for automatically venting the valve chamber to prevent occurrence of a pressure lock condition.
Another telescoping valve seat assembly gate valve is shown in U.S. Pat. No. 5,201,872, issued Apr. 13, 1993, to M. L. Dyer, assigned to Worldwide Oilfield Machine, Inc., which is also incorporated herein by reference, that discloses a gate valve wherein bore pressure in the body cavity of the valve is isolated in the open and closed position. In the closed position, a double metal sealing barrier is provided across the gate. In the open position, the pressure is isolated from the stem packing and bonnet gasket by the seats on either side of the gate. Formation of hydrates in the body cavity is eliminated, and better retention of body grease is achieved during flow through the valves. Metal-to-metal seal surfaces are developed, thereby eliminating wear on the nonmetal components and reducing torque requirements.
U.S. Pat. No. 4,741,509, issued May 3, 1988, to Bunch et al., developed at Worldwide Oilfield Machine, Inc., discloses a gate valve with a body having a valve member and gate chamber, passages communicating through the body into the chamber, a recess in the body surrounding the opening of each passage into the chamber, a bushing positioned in each recess, a gate positioned within the chamber, means for moving the gate within the chamber between positions communicating flow between the passages and closing flow between the passages, inner and outer unidirectional seals positioned between the surface of each recess facing the gate and the opposing surface of the bushing in the recess; each seal includes a U-shaped lip sealing element and a U-shaped spring positioned within the lip sealing element and urging the legs of the element apart into sealing engagement between the bushing and the body; the inner seal, which is positioned closest to the passage, has the open end of its sealing element facing the passage; and the outer seal, which is farther from the passage than the inner seal, has the open end of its sealing facing away from the passage; each seal and the body that has a depth less than the height of the seal while it is still in an effective sealing condition, the seals being compressible in height so that their bushings engage the body recess in a metal-to-metal seal when they are loaded and recoverable from such compressed position to provide a tight seal when the loading is relieved.
U.S. Pat. No. 6,260,822, issued Jul. 17, 2001, to D. Sudhir Puranik, developed at Worldwide Oilfield Machine, Inc., discloses a seat assembly including preferably telescoping seating elements for use between a gate and a pocket in a gate valve body. A seal is provided between the telescoping seating elements that is axially moveable and acts to seal with one or more sloping surfaces disposed on the seating elements. A spring acts to bias the seal toward the sloping surfaces so as to provide an initial seal. The sloping surfaces prevent movement of the seal in one axial direction. As line pressure increases, the seal will move against the sloping surfaces with increased force to maintain the seal between the line or valve bore and the bonnet of the valve. A reverse pressure differential across the seal that is greater than the biasing force will cause the seal element to move in the opposite axial direction and bleed off the pressure across it. The seal may be metallic or have a metal core with a coating of substantially non-elastic, non-permeable, chemically inert material of the type that is resistant to well bore fluids and other chemicals unaffected by substantial changes in temperature.
U.S. Pat. No. 6,279,875, issued Aug. 28, 2001, to Vijay R. Chatufale, developed at Worldwide Oilfield Machine, Inc., discloses a gate valve having a telescopingly interfitted seat assembly that fits into a recess in a gate chamber between the gate valve body and the gate. A sealing cavity is formed between two seat elements that form the telescopic connection. A preferably unidirectional seal is disposed therein having two lip seals. The unidirectional seal is preferably oriented to allow leakage for a pressure differential wherein the gate chamber has a higher pressure than the pressure on the opposite side of the seal from the gate chamber. The seal is preferably made of non-permeable material and the material is preferably flexible but non-elastic with little or no memory. Additional such seals may be used for sealing with the gate valve body. In one embodiment, an expansion member is provided for extending into an open end of the seal to expand the two lip seals. An additional bi-directional seal may be provided that is sized to allow leakage when the two seat elements are expanded and to seal when a preferably floating gate compresses one of the telescoping sets seat elements.
U.S. Pat. No. 6,345,805, issued Feb. 12, 2002, to Vijay R. Chatufale and developed at Worldwide Oilfield Machine, Inc., discloses a rotary plug valve that has two telescoping seat assemblies that fit into respective recesses provided in the valve body surrounding a passageway through the plug valve. A valve chamber is formed in the valve body into which the rotary plug may be positioned to control flow through the valve by rotation thereof. In a preferred embodiment, the telescoping seat assemblies provide an upstream and a downstream seal with the rotary plug. The telescoping seat assemblies preferably function differently when in the open and closed position so that both assemblies expand when in the open position whereas in the closed position one assembly expands and one is compressed. A line pressure surface is provided to provide a force against the plug seal seat element. The plug seal seat element and plug mate with a curved surface and the contact stress varies depending on the location along the curved surface. The line pressure surface is made large enough so that a sufficient portion of the mating surface has a contact stress greater than line pressure so as to form a fluid tight, e.g., gas tight, seal. In one preferred embodiment, the line pressure surface is made large enough so that the average contact stress is greater than line pressure. In another embodiment, the seals are comprised of a non-permeable material that is sufficiently flexible to conform to sealing surfaces.
Various types of seals have been utilized in valves and hydraulic systems.
U.S. Pat. No. 6,494,465, issued Dec. 17, 2002, to John Wentworth Bucknell, discloses a seal for hydraulic assemblies operating at high temperatures having adaptations for low pressures sealing and configured to move across the gap to be sealed at higher pressures with an angled base on a slope or a cup shape nested into a groove. The seal at the point of the gap being an elastic, metallic material.
U.S. Pat. No. 6,123,340, issued Sep. 26, 2000, to Sprafka et al., discloses a seal for use in a modular flow device and is utilized for joining and aligning a first mating surface and second mating surface having axial flow passageways. The seal comprises a protruding annular radiused edge about the axial passageway of the first mating surface and an annular groove about the axial passageway of the second mating surface. The groove has an inner angled wall for engaging with the annular radiused edge when the mating surfaces are compressively joined. Thus, a leak proof seal is formed around the fluid passageway and the passageways are aligned with respect to each other. The invention also relates to check valves for use with modular surface mount systems in which the check valve can be used as a surface-mounted component or as part of a substrate that is mounted to or between other substrates and components.
U.S. Pat. No. 5,639,102, issued Jun. 17, 1997, to Peter Ilesic, discloses a sealing arrangement for sealing a conduit for a gaseous or liquid agent that includes a closable housing which fits sleeve-like around the conduit. A sealing member comprising elastomer material is arranged in the housing in an annular configuration therein and has an annular bead which projects toward the wall of the conduit. The bead has a sealing surface to be applied against the wall. The sealing member has an annular gap which subdivides the annular bead in the axial direction of the arrangement into a first radial bead portion at the inward side of the seal and a second radial bead portion at the outward side of the seal. The gap extends from the sealing surface into the annular bead at such an inclination that an acute-angled sealing lip is formed on the second bead portion adjoining the gap. At the inward side of the seal, the first bead portion can have an axially facing annular groove of an undercut configuration which on the first bead portion forms an acute-angled sealing lip which is directed inwardly of the seal.
U.S. Pat. No. 5,431,415, issued Jul. 11, 1995, to Millonig et al., discloses a seal element for installation in an annular groove having a mouth, first and second radial surfaces, and an axial surface therebetween. The seal element has a first radial surface which forms an acute heel angle with the groove first radial surface, and the seal element forms an inner static area adjacent the groove axial surface and first radial surface. Upon installation of a rod and low pressure application, the seal element is compressed into the groove, and the seal element first radial surface is moved into contact with the groove first radial surface. Thus, the seal element prevents contamination from entering into the inner static area. The seal element has first and second angled surfaces forming a high pressure sealing line and third and fourth angled surfaces forming a low pressure sealing line with a stress-relieving radius interconnecting the second and third angled surfaces. When the seal element is positioned in the groove, the angled surfaces face in the direction of and partially protrude through the groove mouth. The stress-relieving radius relieves excessive tensile stress, thereby alleviating the problem of cracking at the sealing face and premature seal failure. Moreover, the stress-relieving radius provides better flexing motion to the low pressure sealing lip, thereby avoiding high compressive stress and reducing the compressive set on the low pressure sealing lip.
U.S. Pat. No. 5,139,274, issued Aug. 18, 1992, to Gaven S. Oseman, discloses a hydraulic seal for sealing between two hydraulic components that move axially one within the other that comprises a first pressure-energized ring seal located between the components so as to respond to hydraulic pressure on an axially directed inner face of the seal, and a second ring seal located adjacent the inner face of the first seal so as to control the flow of hydraulic fluid to the first seal. The second ring seal is located in an annular groove in one of the components with an outer annular face that is directed axially toward the first seal and lies opposite an adjacent side wall of the groove to be supported thereby. A sealing lip protrudes from the groove and has a radially directed annular sealing face to engage in face-to-face contact with the other of the components. An annular inner face of the second ring seal is angled within the groove away from an adjacent side wall of the groove and toward the sealing lip so that the sealing lip can flex within the groove away from the first seal to release excess pressure between the first and second seals.
U.S. Pat. No. 4,372,530, issued Feb. 8, 1983, to Carl F. Livorsi, discloses a butterfly valve which is disposed in a valve body for sealing engagement with a resilient seat ring disposed in a tapered groove defined by the valve body and a retaining ring. A metallic back-up ring is disposed between two legs of the seat ring to support a sealing portion thereof when the valve is closed. Flanges on the legs retain the seat ring together with the backup ring in the groove. Parallel walls at the bottom of the groove insure seat ring and back-up ring retention. An “O” ring is disposed between the back-up ring, the flanges and the groove bottom and pressurized fluid passageways are provided to produce a two-way pressure assist for sealing.
U.S. Pat. No. 4,353,525, issued Oct. 12, 1982, to Robert A. DiDomizio, Jr., discloses a rotary valve which has a fluid seal ring which is loosely captured within a valve body and provides a fluid seal at a peripheral edge of a movable member selectively positionable in a fluid conduit. The seal ring has an annular coaxial recess located on an inner side face thereof. A fixed valve seat member retained in the valve body coaxially with the seal ring has an outwardly projecting cantilever beam in the form of an integral annular ring located on a side face thereof. The end of the cantilever beam is provided with a tapered face arranged to cooperate with a tapered wall surface defining a side of the recess within the seal ring. The contact between the tapered side face of the cantilever beam and the tapered recess surface provides a fluid seal which is selectively positionable along the tapered recess surface to permit a self-aligning action of the seal ring to accommodate varying mechanical eccentricities of the seal ring in its fluid sealing position.
U.S. Pat. No. 4,252,352, issued Feb. 24, 1981, to John B. Scannell, discloses a sealing ring for a rotary shaft. The sealing ring has a planar frusto-conical configuration and is received in an obliquely slanted groove provided in either the rotary shaft or the bearing surface surrounding the shaft. The use of an obliquely slanted groove causes seal contact over a wide area on the rotary shaft reducing heat buildup, while the frusto-conical configuration insures that the lips of the seal are in firm continuous circumferential contact with the shaft. Oblique mounting of the sealing ring also causes axial flow of the fluid being sealed and the formation of a fluid annulus adjacent the seal and on the pressure side thereof. Selective positioning of a plurality of obliquely mounted sealing rings results in the formation of complementary annuli and the axial flow of fluid between adjacent sealing rings.
U.S. Pat. No. 3,090,630, issued May 21, 1963, to Fred Gasche, discloses a high pressure joint which can be taken apart and put back together again many times without changing the gaskets. The joint has a resilient metal gasket, usually of the same metal as the body and cover, with narrow annular sealing lands on the upper and lower surfaces occupying only a fraction of the radial width of the gasket. The lands converge toward each other in a radially outward direction at an acute angle and seal against mating converging surfaces of the cover and body. If the cover and body should separate, sealing contact is maintained by radial expansion of the gasket.
Thus, in some cases, the present invention provides for the possibility of de-energizing seals during operation of the valve bonnet in a manner not shown by the prior art. In another application, it would be desirable if the downstream seat assembly were constructed to provide a backup seal if the upstream seat assembly were to fail. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems.